1. Field of the Invention
The present invention refers to an apparatus for absorbing energy to attenuate a force caused by an impact. In particular, it refers to a triggering system for the plastic collapse of a metal structural element, particularly suitable for attenuating forces generated by high-velocity impacts, such as in the case of aircraft accidents.
2. Description of the Related Art
Various devices have been produced in the past in order to minimize damage to people and vehicles caused by possible high-velocity impacts of aircraft. Such devices are based on the failure of metal elements, and some include a particular apparatus for triggering the collapse of the element provided for absorbing energy.
U.S. Pat. No. 3,997,133 describes landing gear that includes an energy absorbing element coaxial to the cylinder of the shock strut. The cylinder is secured to a connection structure of the fuselage by a frangible fitting constituted by a system of weakened bolts. When the failure force of the bolts is reached, a system of flanges coupled to the cylinder engages the sacrificial energy absorbing element working it plastically so as to cut it into longitudinal strips.
U.S. Pat. No. 5,547,148 describes a landing gear that includes an expendable element coaxial to the cylinder of the shock strut. The cylinder is fixed to a connection structure of the fuselage by a load control system made of a trunnion fitted with flanges, designed to fail at a certain level of axial force transmitted by the system. The expendable element is represented by a tube which, with the failure of the flanges, is engaged by a conical surface that deforms it, gradually buckling its walls outwards and fracturing them.
U.S. Pat. No. 6,308,809 describes a system for absorbing energy based on the plastic deformation of a thin-walled tube. A conical mandrel engages the tube, applying a pressure on the walls which is outwardly directed. The tube becomes plastic and successively gradually collapses fracturing along longitudinal lines.